An optical fiber ribbon cable having loose tube optical units and a method of manufacturing the same

Abstract

The application discloses an optical fiber ribbon cable with loose tube optical units and a preparation method thereof. The optical fiber ribbon cable with loose tube optical units comprises a loose tube, a composite ribbon and an ointment arranged in the loose tube. The composite ribbon comprises an optical fiber ribbon and two protective ribbons. The optical fiber ribbon is in a spiral shape, and the optical fiber ribbon has a spiral inner side and a spiral outer side. The two protective ribbons are arranged on the spiral inner side and the spiral outer side of the optical fiber ribbon. The application adopts the protective ribbons with the same width as the optical fiber ribbon, so that the optical fiber ribbon in the loose tube is not directly in contact with the inner wall of the sleeve, the transmission direction and distribution of asymmetrically distributed stress are changed, better protection is provided, the edge fiber in the optical fiber ribbon matrix is prevented from being pressed by stress, the transmission loss difference between the edge fiber and the middle fiber is reduced, and the application is beneficial to reducing defective products and improving the compression resistance of the sleeve and the optical cable.

Description

Technical Field

[0001] This invention belongs to the field of optical cables, and more specifically, relates to an optical fiber ribbon cable with loose tube optical units and its preparation method. Background Technology

[0002] Fiber optic ribbon cable refers to an optical cable whose core fiber adopts a fiber ribbon structure. Fiber optic ribbon cores are mostly used in central tube or skeleton-type optical cables. When fiber optic ribbon cables are spliced ​​using a ribbon fiber fusion splicer, the fibers of one fiber ribbon can be fused together in one go, thus greatly improving splicing efficiency. The more cores in each fiber ribbon, the higher the splicing efficiency. Fiber optic ribbon cables are commonly used in large and medium-sized metropolitan area networks (MANs) for fiber optic cable sections with a large number of cores (no less than 72 cores), such as the core layer and access layer backbone sections of MANs.

[0003] Existing fiber optic ribbon cables with loose tube structures involve placing a certain number of fiber ribbons inside the loose tube. These fiber ribbons are stacked together to form a fiber ribbon array. Since the loose tube is a circular structure, the fibers located at the four vertices of the fiber ribbon array are easily rubbed and squeezed by the inner wall of the tube, resulting in increased attenuation or even damage to the fibers at the corners. Therefore, the tube needs to have sufficient internal space. This results in low utilization of the internal space, which is not conducive to tube diameter and cost control, and makes it difficult to obtain high fiber core density. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides an optical fiber ribbon cable with a loose tube optical unit. Its structure is reasonably set, which helps to protect the optical fiber in the optical fiber ribbon from increased attenuation due to stress. Moreover, the loose tube and optical cable have small diameters, resulting in low product cost.

[0005] To achieve the above objectives, according to one aspect of the present invention, an optical fiber ribbon cable with a loose tube optical unit is provided, comprising a loose tube and a composite tape and grease disposed within the loose tube.

[0006] The composite strip includes an optical fiber strip and two protective strips;

[0007] The optical fiber ribbon is spiral in shape, and thus has a spiral inner surface and a spiral outer surface.

[0008] The protective strip is provided in two parts, one of which covers the spiral inner surface of the optical fiber strip and the other covers the spiral outer surface of the optical fiber strip.

[0009] Both the optical fiber strip and each of the protective strips are rectangular parallelepipeds when flattened.

[0010] When the optical fiber ribbon and each of the protective ribbons are in a flattened state, the optical fiber ribbon has the same width as the protective ribbon, so that after the protective ribbon is installed on the optical fiber ribbon, the protective ribbon completely covers the optical fiber ribbon.

[0011] Preferably, in the optical fiber ribbon cable, the bending modulus of the protective strip is less than that of the optical fiber ribbon.

[0012] Preferably, the flexural modulus of the protective strip of the optical fiber ribbon cable is between 100 MPa and 500 MPa.

[0013] Preferably, in the optical fiber ribbon cable, the edge of the protective strip in the width direction is flush with the edge of the optical fiber ribbon in the width direction.

[0014] Preferably, the protective strip of the optical fiber ribbon cable is made of PET plastic.

[0015] Preferably, the loose tube of the optical fiber ribbon cable is made of PBT, PP, TPEE or PC material, and has an outer diameter of 6mm to 15mm.

[0016] Preferably, the optical fiber ribbon cable has 1 to 24 optical fibers. When there is more than one optical fiber ribbon, these optical fibers are stacked together in an array, and each optical fiber ribbon has 4 to 24 optical fibers.

[0017] Preferably, in the optical fiber ribbon cable, the thickness of the protective strip is 0.1mm to 0.2mm, and the thickness of the protective strip is less than the thickness of the optical fiber ribbon.

[0018] Preferably, in the optical fiber ribbon cable, there is a gap between the composite ribbon and the inner wall of the loose tube.

[0019] According to another aspect of the present invention, a method for preparing the aforementioned optical fiber ribbon cable is provided, comprising the following steps:

[0020] The width of the protective strip is pre-made to be the same as the width of the optical fiber strip;

[0021] Using a molding die, protective tape is attached to both sides of the fiber array in the direction of fiber stacking to form a fiber ribbon array with protective tape.

[0022] This causes the fiber array with the protective band to spiral and enter the loose tube;

[0023] The loose tube is used to make the cable core and then to form a cable.

[0024] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0025] This invention uses a protective strip with the same width as the optical fiber ribbon, so that the optical fiber ribbon in the loose tube will not directly contact the inner wall of the tube, changing the transmission direction and distribution of the asymmetrical stress, providing better protection, avoiding the side fibers in the optical fiber ribbon matrix from being subjected to compressive stress, reducing the difference in transmission loss between the side fibers and the middle fibers, which is beneficial to reduce defective products and improve the compressive strength of the tube and optical cable.

[0026] Because of the protective band, the optical fiber is less prone to increased attenuation due to stress, so it does not need a large buffer space. The internal space of the loose tube can be kept as small as possible, which helps to reduce its diameter and lower product costs. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention.

[0028] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: .1-protective tape, 2-fiber optic ribbon matrix, 3-grease, 4-loose tube. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] Reference Figure 1 An optical fiber ribbon cable with a loose tube optical unit includes a loose tube 4 and a composite tape and grease 3 disposed inside the loose tube 4. The loose tube 4 is made of PBT, PP, TPEE or PC material and has an outer diameter of 6mm to 15mm. The composite tape includes an optical fiber tape 2 and two protective tapes 1.

[0031] The optical fiber strip 2 is spiral in shape, and thus has a spiral inner surface and a spiral outer surface.

[0032] The protective strip 1 is provided with two strips, one of which covers the spiral inner surface of the optical fiber strip 2 and the other covers the spiral outer surface of the optical fiber strip 2.

[0033] Both the optical fiber ribbon 2 and each of the protective ribbons 1 are rectangular in shape when flattened. When flattened, the optical fiber ribbon 2 has the same width as the protective ribbon 1, so that after the protective ribbon 1 is installed on the optical fiber ribbon 2, its edge in the width direction is flush with the edge of the optical fiber ribbon 2 in the width direction. This allows the protective ribbon 1 to completely cover the optical fiber ribbon 2, achieving full coverage. When the composite ribbon is spiral-shaped, the inner and outer surfaces of the optical fiber ribbon 2 are completely covered by the protective ribbon 1 and are not exposed. Thus, when the composite ribbon contacts the inner wall of the loose tube 4, and the loose tube 4 compresses the composite ribbon, it is the protective ribbon 1 that directly contacts the inner wall of the loose tube 4, not the optical fiber ribbon 2. The protective ribbon 1 is preferentially compressed by the inner wall of the tube before the optical fiber ribbon 2, and the protective ribbon 1 as a whole can resist the force of the loose tube 4, thereby protecting the optical fiber ribbon 2.

[0034] The optical unit with loose tubes and fiber ribbon 2 as the light guiding element has the characteristics of an outer circle and an inner square. However, although the overall structure is symmetrical, the stress transmission is asymmetrical. The stress distribution on any cross-section of the optical unit is symmetrical, and the magnitude and probability of stress in each direction are the same. However, the stress transmitted to the fiber array is concentrated in the fibers at the four corners of the array, and the symmetry is worse than that of the stress borne by the loose tube. When the stress is transmitted to the fiber ribbon 2 array, the fiber ribbon 2 array has two dimensions: the fiber ribbon 2 direction and the fiber ribbon 2 stacking direction. In the fiber ribbon 2 stacking direction, because the fiber ribbons 2 are relatively loose, and the fiber ribbons 2 are connected by parallel resin with a high bending modulus, the stress on the fiber ribbon 2 array mainly causes the side fibers at the four corners of the array to bend, further causing stress asymmetry. The transmission loss of the side fibers at the four corners of the fiber ribbon 2 is significantly higher than that of the fibers at other positions.

[0035] Even with armored elements such as longitudinal water-blocking tape covering the surface of the fiber ribbon array, the asymmetrical stress transmission distribution cannot be changed, and the problem of significant differences in transmission loss between the side fiber and the middle fiber cannot be solved.

[0036] This invention addresses the problem of asymmetrical stress distribution in the fiber optic ribbon 2 array by not employing a stress dispersion strategy. Instead, it leverages the characteristic of uneven stress distribution by adding a protective strip 1 along the stacking direction of the fiber optic ribbons 2. The flexural modulus of the protective strip 1 is lower than that of the fiber and the resin. The fiber optic ribbon 2 array does not directly receive the deformation stress from the loose tube; instead, it is conducted through the protective strip 1. Since the flexural modulus of the protective strip 1 is smaller, or even much smaller, than that of the fiber optic ribbon 2 and the resin, the unevenly distributed stress preferentially causes deformation in the protective strip 1 and is absorbed. In particular, the deformation of the protective strip 1 along the fiber optic ribbon 2 direction has a significant effect on reducing stress. By changing the direction of stress-induced deformation from primarily causing deformation of the fiber along the stacking direction of the fiber optic ribbons 2 to primarily causing deformation of the fiber protective strip 1 along the fiber optic ribbon 2 direction, the stress is more fully absorbed by the protective strip 1. Therefore, the stress borne by the four corners of the fiber optic ribbon 2 array towards the edge fibers is reduced, and the difference between the stress and the micro-bending deformation of the middle fibers is not significant, thereby reducing the difference in transmission loss between the edge fibers and the middle fibers.

[0037] Based on the above principles, setting the relative position of the guard band 1 and the fiber band 2 is crucial. The guard band 1 needs to be positioned along the stacking direction of the fiber band 2. If it is positioned along the direction of the fiber band 2, i.e., on the side of the array of guard band 1 and fiber band 2, its ability to reduce the deformation of the fiber band 2 along the stacking direction will be weak. Furthermore, a fully enclosed arrangement, such as longitudinal wrapping or wrapping, cannot be adopted. While a fully enclosed arrangement of the guard band 1 can reduce the stress effect to some extent through the deformation of the guard band 1, it cannot reduce the stress difference by changing the direction of the stress-induced deformation. In particular, a fully enclosed arrangement will further restrict the relaxation state of the fiber and may even lead to increased transmission loss. Simultaneously, the difference in bending modulus between the guard band 1 and the fiber band 2 is another key factor in coordinating their relative positions. If the bending modulus of the guard band 1 is large, comparable to that of the fiber band 2, it cannot absorb stress well and will instead transmit stress, still causing edge fiber deformation, thus limiting its ability to reduce stress effects. If the bending modulus is too small, it cannot effectively change the stress transmission direction, and the stress borne by the edge fiber will still lead to a significant difference in transmission loss between the edge and the middle fiber.

[0038] In addition, the width of the protective tape must cover the edge fibers, but should not exceed them; ideally, it should be flush with the edge fibers. If it does not cover the edge fibers, it will not be able to bear the stress as a substitute for the edge fibers. If it exceeds the edge fibers, it will bend in the loose tube, which will weaken the protective tape's ability to change the direction of stress transmission.

[0039] Experiments show that when the bending modulus of the protective tape 1 is between 100MPa and 500MPa, it can effectively reduce the difference in transmission loss between the side fiber and the middle fiber, and the overall transmission loss is reduced.

[0040] Preferably, the protective strip 1 is made of PET plastic (PET (polyethylene terephthalate), i.e., polyester resin), which is equivalent to replacing the optical fiber strip 2 in bearing the stress from the loose tube 4.

[0041] Furthermore, the number of optical fiber strips 2 is 1 to 24. When there is more than one optical fiber strip 2, these optical fiber strips 2 are stacked together in an array, and the number of optical fibers in each optical fiber strip 2 is 4 to 24. The protective strip 1 covers the innermost and outermost optical fiber strips 2.

[0042] Furthermore, the thickness of the protective strip 1 is 0.1mm to 0.2mm, and the thickness of the protective strip 1 is less than the thickness of the optical fiber strip 2.

[0043] Furthermore, there is a gap between the composite tape and the inner wall of the loose sleeve 4, so that the loose sleeve 4 will not continuously squeeze the composite tape.

[0044] The loose tube 4 of this invention is filled with grease 3, and an optical fiber ribbon 2 is placed inside the loose tube 4. Preferably, 12 optical fiber ribbons 2 are stacked together. Each optical fiber ribbon 2 preferably has 12 cores, a width of 3.1 mm, and a thickness of 0.3 mm. A protective strip 1 is placed on the inner and outer sides of the optical fiber ribbon 2. The protective strip 1 is easily identifiable white or black, with a thickness of 0.2 mm and a width of 3.1 mm. The composite strip formed by the two protective strips 1 and the optical fiber ribbon 2 is twisted into a spiral shape. The optical fiber in the optical fiber ribbon 2 does not directly contact the inner wall of the loose tube 4, avoiding the increase in attenuation caused by stress. Therefore, the distance between the optical fiber ribbon 2 and the inner wall of the loose tube 4 can be minimized. The outer diameter of the loose tube 4 is preferably 6.5 mm, which can be 1 mm to 2 mm smaller than the conventional size. If this loose tube 4 is used to produce optical fiber ribbon 2 optical cables with stranded structure or central tube structure, the outer diameter of the optical cable can be 2 mm to 6 mm smaller than the conventional size, which can significantly reduce product costs while ensuring quality.

[0045] The method for preparing optical fiber ribbon cable provided by the present invention includes the following steps:

[0046] The width of the protective strip is pre-made to be the same as the width of the optical fiber strip;

[0047] Using a molding die, protective tape is attached to both sides of the fiber array in the direction of fiber stacking to form a fiber ribbon array with protective tape.

[0048] The fiber array with protective band is spiraled and enters the loose tube; the loose tube is simultaneously filled with design elements, such as grease, water-blocking yarn or water-blocking powder.

[0049] The loose tube optical unit is used to manufacture the cable core and form a cable.

[0050] The following is an example:

[0051] The following section uses a 12-core fiber optic ribbon as an example to describe in detail the performance of the fiber optic ribbon cable with loose tube optical units provided by this invention.

[0052] The fiber optic ribbon cable structure provided in the embodiment is as follows:

[0053] Reference Figure 1 An optical fiber cable with an optical fiber ribbon 2 includes a loose tube 4 and a composite tape and grease 3 disposed inside the loose tube 4. The loose tube 4 is made of PBT and has an outer diameter of 10 mm. The composite tape includes an optical fiber ribbon 2 and two protective tapes 1.

[0054] The optical fiber strip 2 is spiral in shape, and thus has a spiral inner surface and a spiral outer surface.

[0055] The protective strip 1 has two sections, one covering the inner spiral surface of the optical fiber strip 2 and the other covering the outer spiral surface of the optical fiber strip 2. The optical fiber strip is 3.1 mm wide and 0.3 mm thick. The protective strip 1 is placed on the inner and outer surfaces of the optical fiber strip 2, and is easily identifiable in white or black, with a thickness of 0.2 mm and a width of 3.1 mm.

[0056] The thickness of the protective strip 1 is 0.15, and the thickness of the protective strip 1 is less than the thickness of the optical fiber strip 2.

[0057] Furthermore, there is a gap between the composite tape and the inner wall of the loose sleeve 4, so that the loose sleeve 4 will not continuously squeeze the composite tape.

[0058] The loose tube 4 of the present invention is filled with grease 3, and an optical fiber ribbon 2 is placed inside the loose tube 4. The outer diameter of the loose tube 4 is preferably 6.5 mm.

[0059] The parameters of the protective tape and the performance tests of the optical cable are shown in Table 1:

[0060] Table 1

[0061]

[0062] The only difference between the comparative example and the embodiment is the material and performance of the protective strap; the other structures and parameters are the same as those in the embodiment.

[0063] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An optical fiber ribbon cable, comprising a loose tube and a composite tape and grease disposed within the loose tube, characterized in that: The composite ribbon includes an optical fiber ribbon array and two guard ribbons, with the optical fiber ribbons stacked together to form the optical fiber ribbon array; The fiber optic ribbon array is spiral in shape, and the fiber optic ribbon has a spiral inner surface and a spiral outer surface. A protective strip is disposed in the direction of fiber optic ribbon stacking. Two protective strips are provided, one of which covers the inner spiral surface of the fiber optic ribbon and the other covers the outer spiral surface of the fiber optic ribbon. Both the optical fiber ribbon and each of the protective ribbons are rectangular in shape when flattened; the bending modulus of the protective ribbon is less than that of the optical fiber ribbon. When the optical fiber ribbon and each of the protective strips are in a flattened state, the optical fiber ribbon has the same width as the protective strip, and the edge of the protective strip in the width direction is flush with the edge of the optical fiber ribbon in the width direction, so that after the protective strip is installed on the optical fiber ribbon, the protective strip completely covers the optical fiber ribbon.

2. The optical fiber ribbon cable according to claim 1, characterized in that, The flexural modulus of the protective belt is between 100 MPa and 500 MPa.

3. The optical fiber ribbon cable according to claim 1, characterized in that, The protective strip is made of PET plastic.

4. The optical fiber ribbon cable according to claim 1, characterized in that, The loose sleeve is made of PBT, PP, TPEE or PC material, with an outer diameter of 6 mm to 15 mm.

5. The optical fiber ribbon cable according to claim 1, characterized in that, The number of optical fiber ribbons is 1 to 24. When there is more than one optical fiber ribbon, these optical fiber ribbons are stacked together in an array, and the number of optical fibers in each optical fiber ribbon is 4 to 24.

6. The optical fiber ribbon cable according to claim 1, characterized in that, The thickness of the protective strip is 0.1 mm to 0.2 mm, and the thickness of the protective strip is less than the thickness of the optical fiber strip.

7. The optical fiber ribbon cable according to claim 1, characterized in that, There is a gap between the composite tape and the inner wall of the loose sleeve.

8. The method for preparing an optical fiber ribbon cable as described in any one of claims 1 to 7, characterized in that, Includes the following steps: The width of the protective strip is pre-made to be the same as the width of the optical fiber strip; Using a molding die, a protective strip is attached to both sides of the fiber ribbon array in the direction of fiber ribbon stacking to form a fiber ribbon array with a protective strip. This causes the fiber optic strip array with the protective band to spiral and enter the loose tube; The loose tube optical unit is used to manufacture the cable core and form a cable.

Images